CN101997588A - Method and device for transmitting signal in multi-antenna system - Google Patents

Abstract

Embodiments of the present invention provide a method and device for signal transmission in a multi-antenna system, wherein the method includes: performing Alamouti encoding on each group of common channel symbols to form two branches; selecting different weight vectors for different branches Beamforming, to obtain the transmitted signal of each branch on each antenna, the beam patterns corresponding to different weight vectors are irrelevant, and the peak-to-average power ratio in the angle dimension is lower than the preset threshold; the two branches The transmit signals on each antenna are superimposed and transmitted. The embodiment of the present invention provides the introduction of the Alamouti code, utilizes the independence of the two virtual channels to generate space diversity gain, and enhances the performance of comprehensive coverage of the common channel of the multi-antenna system.

Description

A method and device for signal transmission in a multi-antenna system

technical field

Embodiments of the present invention relate to the field of communications, and in particular to a method and device for transmitting signals in a multi-antenna system.

Background technique

Since the 1990s, the wireless communication industry has experienced explosive growth. With voice, data, video and other services gradually becoming mobile, the demand for bandwidth of wireless communication systems is getting higher and higher. However, the available frequency band resources are becoming increasingly scarce, so how to improve spectrum utilization has become a key issue in wireless communication research.

Technologies that can effectively improve spectrum utilization include: multiple access, signal detection, modulation, and channel coding, etc. Among them, the potential of multiple antenna systems (MAS, Multiple Antennas System) is increasingly important in wireless communications.

Smart Antenna (SA, Smart Antennas), also known as Antenna Array System (AAS, Antenna Array System), is a kind of multi-antenna system. The array element spacing of smart antennas is generally smaller than the correlation distance of the channel. Utilizing the signal correlation between the antenna elements, beamforming can be realized, and the high-gain narrow beam can be adaptively pointed to the mobile terminal in communication, and the null trap can be adjusted to align with the interference direction.

Figure 1 is a typical smart antenna system structure. The smart antenna array for narrowband signals includes M>1 antenna elements, m is one of the M antenna elements, M receiving antennas correspond to M receiving channels, and M transmitting channels correspond to M transmitting antennas.

For a specific user, the direction of arrival estimation module (DOA estimation) estimates the direction of arrival information of the specific user according to the received signals on the M antenna array elements. The adaptive beamforming weight coefficient generator adjusts the weight vector (adaptive beamforming weight coefficient generator) according to the direction of arrival information of the specific user, and generates a weighting coefficient for each transmission channel, and the weight coefficient adjuster of each channel uses The weighting coefficient of its own channel adjusts (multiplies) the dedicated channel signal s(t), and the weighting coefficients w1, w2...wM of M antenna array elements form a weight vector w, thereby forming a directional beam for the specific user, and Adaptively track user's movement. In the figure * is the conjugate symbol.

Multiple Input Multiple Output (MIMO, Multiple Input Multiple Output) is another form of multi-antenna system. Foschini has theoretically proved the great potential of this technology to improve spectrum utilization, and its channel capacity increases linearly with the number of antennas (proportional to minimum number of antennas at the transceiver end). MIMO technology can also be regarded as a kind of smart antenna. The main difference is that the antenna element spacing is different, and the antennas of the MIMO system should generally maintain no correlation.

In a cellular mobile communication system, a base station allocates a dedicated channel (Dedicated Channel) to each active user in a cell/sector to carry voice, data or video services. A base station based on multiple antennas can apply techniques such as beamforming or precoding on dedicated channels to transmit signals for specific users and reduce interference to other users.

In an actual mobile communication system, in addition to the dedicated channel in the cell/sector, a public channel (Public Channel) is also required; the public channel carries the public information required by all mobile terminals in the cell/sector, such as the broadcast channel System information, reference signals in the synchronization channel, pilots in the forward access channel (FACH, Forward Access Channel), paging and public control messages, etc. The requirements of public channels for base station system coverage are quite different from those of dedicated channels. It is required that all mobile terminals in a cell/sector can receive signals at the same time, so the base station needs to have a good overall cell/sector coverage for the entire cell/sector. area coverage.

In the prior art, there is a solution for full cell/sector coverage of antenna arrays, which divides the transmission time of common channel signals into time slots, selects a set of weight vectors with complementary patterns, and alternates them in consecutive time slots Complementary weight vectors are used to achieve full cell/sector coverage based on smart antennas.

In the above technique, although multiple complementary weight vectors are alternately used, since the number of weight vectors is limited and the pattern corresponding to each weight vector is fixed, the average antenna gain of multiple pattern is in different directions They are not completely equal, but only approximately isotropic, resulting in a relatively large difference in bit error rate (BER, Bit Error Rate) performance in each direction, and the performance of full coverage of public channels needs to be improved.

Contents of the invention

Embodiments of the present invention provide a method and device for signal transmission in a multi-antenna system, which can realize full coverage of common channels in the multi-antenna system.

An embodiment of the present invention provides a method for signal transmission in a multi-antenna system, including:

Alamouti encoding is performed on each group of common channel symbols to form two branches; for different branches, different weight vectors are selected for beamforming, and the transmitted signals of each branch on each antenna are obtained, and different weight vectors The corresponding beam patterns are irrelevant, and the peak-to-average power ratio in the angle dimension is lower than a preset threshold; the two transmit signals branched on each antenna are superimposed and sent.

Correspondingly, an embodiment of the present invention also provides an apparatus for signal transmission in a multi-antenna system, including:

An encoding module, configured to perform Alamouti encoding on each group of common channel symbols to form two branches;

The weight vector acquisition module is used to select different weight vectors for different branches, wherein the beam patterns corresponding to different weight vectors are irrelevant, and the peak-to-average power ratio in the angle dimension is lower than a preset threshold;

The beamforming module is used to perform beamforming on different branches according to the selected weight vector, so as to obtain the transmission signal of each branch on each antenna;

The sending module is used to superimpose and send the two transmitted signals branched on each antenna.

It can be seen from the above technical solution that the embodiment of the present invention introduces Alamouti coding at the transmitting end, utilizes the multi-antenna system to generate two virtual independent channels, utilizes the independence of the two virtual channels, generates space diversity gain, and performs beamforming type, to achieve the same quality of received signals in all directions, and to enhance the performance of the multi-antenna system's comprehensive coverage of public channels.

Description of drawings

FIG. 1 is a schematic diagram of smart antenna beamforming in the prior art;

Fig. 2 is the flow chart of the embodiment of the method for realizing common channel coverage of the present invention;

Fig. 3 is a structural diagram of an embodiment of a device for realizing common channel coverage according to the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Embodiments of the present invention provide a method and device for signal transmission, which can enhance the performance of full coverage of common channels in a whole cell/sector.

The signal sending method in the embodiment of the present invention includes:

1) Alamouti encoding is performed on each group of common channel symbols to form two branches;

In this embodiment, multiple antennas transmit common channel signals. Firstly, symbols of the common channel are divided into groups of two, and Alamouti coding is performed on each group to form two branches.

2) For different branches, select different weight vectors;

After Alamouti coding is performed, different weight vectors are selected for the two branches to perform beamforming to obtain the transmitted signal of each branch on each antenna. The dimension of each weight vector is equal to the number of transmitting antennas, and the two different weight vectors correspond to uncorrelated beam patterns, and the peak-to-average power ratio of the two beam patterns in the angular dimension is lower than a preset threshold.

3) Superimpose and send the two branched symbols after beamforming.

The transmitted signals of the two branches on each antenna are superimposed and sent out.

In this embodiment, two different weight vectors can be regarded as two virtual antennas. Since the two virtual antennas generally have different gains in the same direction, they can be considered uncorrelated. In this embodiment, by introducing Alamouti coding at the transmitting end, a multi-antenna system is used to produce two virtual antennas, and the uncorrelation of the two virtual antennas is used to obtain space diversity gain, and on the basis of achieving consistent signal quality in each receiving direction, the enhanced The performance of multi-antenna system common channel comprehensive coverage is improved.

For ease of understanding, the method for implementing common channel coverage with multiple antennas in the embodiment of the present invention will be described in detail below in conjunction with the accompanying drawings. Please refer to FIG. 2. The method for implementing common channel coverage with multiple antennas in the embodiment of the present invention includes:

201. Divide common channel symbols;

In this embodiment, when there is a signal to be transmitted in the common signal, the common channel symbols can be grouped in pairs, and a group can be expressed as s=[s ₁ , s ₂ ] ^T . The common channel symbols here may be broadcast/multicast bits that have undergone channel coding, interleaving and constellation mapping.

202. Perform Alamouti encoding;

Alamouti encoding specifically performs the following transformation on each group of input symbols s=[s ₁ , s ₂ ] ^T :

$\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; \&Right\; Arrow;</span>\mathrm{<span\; class="notranslate">\; S</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

对应第一空间分路，空间分路也就是虚拟天线；同样，第二行对应第二空间分路。即对于发射符号s，在第一时间-频率资源块上发射s₁和s₂，在第二时间-频率资源块上发射和

每个天线的信道响应在这两个时间-频率资源块的值是高度相关的，并假设为相同。由于一个Alamouti编码块在每一个时间-频率块上只有两个符号，所以每个时间-频率资源块上可以同时传输多个Alamouti编码块，传输的Alamouti编码块的个数取决于时间-频率资源块的大小。(.) ^* means to take the conjugate. Each row of the matrix S corresponds to an antenna element in the space domain, and each column corresponds to a transmission time-frequency resource block in the time-frequency domain. In this example, the first row

Corresponding to the first space branch, the space branch is also the virtual antenna; similarly, the second row Corresponds to the second space shunt. That is, for the transmitted symbol s, s ₁ and s ₂ are transmitted on the first time-frequency resource block, and s 2 are transmitted on the second time-frequency resource block and

The channel response of each antenna at these two time-frequency resource block values is highly correlated and assumed to be the same. Since an Alamouti coding block has only two symbols on each time-frequency block, multiple Alamouti coding blocks can be transmitted simultaneously on each time-frequency resource block, and the number of Alamouti coding blocks transmitted depends on the time-frequency resource block size.

203. Obtain the base weight vector;

In this embodiment, first design a basic weight vector w=[w ₁ w ₂ ... w _M ] ^T , the basic weight vector is composed of M weighting coefficients, and the weighting coefficients are denoted as w _m , m=1, .. ., M, M weighting coefficients correspond to M transmit channels, that is, correspond to M antennas, and M is a positive integer greater than 1.

Here x ^T represents the transpose of x, for example the matrix [w ₁ w ₂ ... w _M ] ^T represents the transpose of the matrix [w ₁ w ₂ ... w _M ].

The coverage angle of the beam generated by the basic weight vector beamforming should reach the preset threshold, the beam flatness should reach the preset threshold, and the peak-to-average power ratio in the angle dimension is lower than the preset threshold, that is to say, the beam should It has the characteristics of wide coverage angle, flat beam, and low peak-to-average ratio. The peak-to-average power ratio on the angle dimension is the maximum value of the power on the angle dimension divided by the average power on the angle dimension.

In order to reduce the cost and avoid the use of high-power amplifiers, so that each power amplifier can be used efficiently, the transmission power of each antenna can be required to be equal, that is, the modulus of each weight coefficient in the corresponding basic weight vector is equal, |w ₁ |= |w ₂ |=...=|w _m |.

204. Acquire the right vector;

For space branch one, select the phase value φ ₁ between 0 and 2π, and calculate the weight vector on branch one according to the formula (2) according to the basic weight vector w

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; diag</span>}\left[\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; j\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}& <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}\end{array}\right]<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; w</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

For space branch two, choose the phase value φ ₂ between 0 and 2π, φ ₂ ≠φ ₁ , and calculate the weight vector on branch two according to formula (3) according to the basic weight vector w

${\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; diag</span>}\left[\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; j\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}& <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\end{array}\right]<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; w</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

More generally, the weight vectors of two branches can be expressed by formula (4), where t represents the sequence number of the branch,

w(t)＝diag[1 e ^jφ(t) e ^j2φ(t) … e ^j(M-1)φ(t) ]w (4)

It can be understood that in practical applications, more ways can be used to transform the base weight vector by using the phase to obtain the weight vector, and the specific way is not limited here.

205. Perform beamforming on each branch to obtain the transmit signal of the branch on each antenna;

The beams generated by the weight vectors corresponding to the two branches need to be complementary in direction. For example, for a linear array, the uncorrelated beams can be expressed as:

${\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; *</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; *</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

表示w_m(t)的共轭，d表示阵元的间距，

Among them, α(θ) represents the direction vector of the antenna array, which is an M-dimensional column vector, θ represents the direction angle between the signal and the antenna array, and the peak-to-average power ratio in the angle dimension is lower than the preset threshold; M represents The number of antennas, w _m represents the weight coefficient on the mth antenna,

Represents the conjugate of w _m (t), d represents the spacing of array elements,

206. Superimpose and send the beamformed signals of the two split beams.

The transmitted signals of the two branches on each antenna are correspondingly added to obtain the transmitted signal on each antenna.

此时，由基权向量得到的两个权向量分别为Assume that the phase values selected by assignment models 1 and 2 are φ ₁ and φ ₂ respectively, and the data after Alamouti space-time coding are

At this time, the two weight vectors obtained from the base weight vector are

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; diag</span>}\left[\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; j\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}& <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}\end{array}\right]\mathrm{<span\; class="notranslate">\; w</span>}\\ {\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; diag</span>}\left[\begin{array}{ccccc}\mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; j\&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}& <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& {\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\end{array}\right]\mathrm{<span\; class="notranslate">\; w</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

For the two symbols of each time-frequency resource block in the coding block, such as [s ₁ , s ₂ ] ^T , its two components are multiplied by two weight vectors containing M elements respectively to obtain two M The two vectors are added to form an M-dimensional vector, which is sent to M transmitting antennas, and each element of the M-dimensional vector formed by the addition corresponds to an antenna of the multi-antenna system, namely

${\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; w</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; diag</span>}\left[\begin{array}{cccc}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>& {\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}& <span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& {\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\end{array}\right]\mathrm{<span\; class="notranslate">\; w</span>}$

(8)

Subsequent transmission signals on each antenna may be transmitted after OFDM modulation.

An Alamouti code involves two time-frequency blocks on which the same weighting coefficients are used for each branch. That is, the shaping patterns (also referred to as beam shapes) of the two virtual antennas on the two time-frequency blocks remain unchanged. For the convenience of expression, we assume that these two time-frequency blocks constitute a frame, and transmit the two coded output symbols of the Alamouti space-time-frequency code in the time-frequency dimension respectively, and use the same set of weight vectors in the same frame after framing, Here the same group contains two different weight vectors φ1 and φ2. The frame here is a generalized frame, which extends the traditional time frame to the time-frequency dimension. Frame the continuous transmitted symbols. If there are more frames, the phase of the next frame can be obtained from the current phase and the incremental phase value between frames, specifically:

φ _p (k) = φ _p + k · δ, p = 1, 2 (9)

Here the next frame is adjacent to the current frame in time-frequency. Among them, k represents the frame number of the transmitted signal, p represents two different shaping modes, and δ is the selected incremental phase value between frames. Corresponding to the initial frame, the phases of the two complementary transformations in the first frame are φ _p (1)=φ _p +δ, p=1,2.

For the receiving end,

After the transmission vector s' obtained by formula (8) passes through the wireless channel, the received signal can be expressed as

r ₁ =(g ₁ s ₁ +g ₂ s ₂ )h+n ₁

(10)

${\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}$

Among them, n ₁ and n ₂ represent Gaussian noise values with zero mean and variance δ ² .

The values of channel fading and beamforming are superimposed. Since g _n , n=1, 2 are independent of each other, two virtual independent channels can be generated, expressed as h=[h ₁ , h ₂ ] ^T =[g ₁ h, g ₂ h] ^T . Define the received signal vector as r=[r ₁ , r ₂ ^* ] ^T , and the noise vector as n=[n ₁ , n ₂ ^* ] ^T , the above formula can be expressed in the following matrix form:

r=Hs+n (11)

Among them, the channel response matrix is defined as:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; *</span>}& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

The space diversity gain of Alamouti coding can be obtained by demodulating the received signal with minimum mean square error MMSE. The demodulation formula is as follows:

s _mmse = (H ^H H + δ ² I) ^-1 H ^H r (13)

The embodiment of the present invention introduces Alamouti coding at the transmitting end, utilizes the multi-antenna system to generate two uncorrelated virtual antennas, generates space diversity gain, and enhances the performance of comprehensive coverage of the common channel of the multi-antenna system.

The following is an introduction to the device for transmitting signals in the multi-antenna system in the embodiment of the present invention. Specifically, in practical applications, the device can be located at the transmitting end such as a base station. Please refer to FIG. 3. The multi-antenna in the embodiment of the present invention realizes public channel coverage One embodiment of the means includes:

An encoding module 301, configured to perform Alamouti encoding on each group of common channel symbols to form two branches;

Here, the common channel symbol may be a data symbol transmitted in the common channel, such as s=[s ₁ , s ₂ ] ^T .

The weight vector acquisition module 302 is configured to select different weight vectors for different branches, wherein the beam modes corresponding to different weight vectors are irrelevant, and the peak-to-average power ratio in the angular dimension is lower than a preset threshold;

The beamforming module 303 is configured to perform beamforming on different branches according to the selected weight vector to obtain the transmission signal of each branch on each antenna;

The sending module 304 is configured to superimpose and send two transmit signals branched on each antenna.

This device embodiment completely corresponds to the above method embodiment, wherein the weight vector acquisition module 302 is used to select the phase φ(t) for each branch, and obtain the weight vector from the base weight vector w through the following formula:

w(t)＝diag[1 e ^jφ(t) e ^j2φ(t) … e ^j(M-1)φ(t) ]w

Among them, t represents the branch number, M represents the number of transmitting antennas, diag[.] represents a diagonal matrix composed of elements in brackets, the modules of each component of the basic weight vector w are equal and the peak-to-average power ratio in the angular dimension is lower than preset threshold.

The device introduces Alamouti coding, uses the multi-antenna system to generate two virtual independent channels, utilizes the independence of the two virtual channels, generates space diversity gain, and enhances the performance of the multi-antenna system's public channel full coverage.

Those of ordinary skill in the art can understand that all or part of the steps in the method of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can be Is read-only memory, disk or CD, etc.

A method and device for implementing common channel coverage provided by multiple antennas provided by the embodiments of the present invention have been introduced in detail above. For those of ordinary skill in the art, based on the idea of the embodiments of the present invention, both the specific implementation and the scope of application There will be changes, and in summary, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. A signal transmission method in a multi-antenna system, comprising: Alamouti encoding is performed on each group of common channel symbols to form two splits; For different branches, different weight vectors are selected for beamforming, and the transmitted signal of each branch on each antenna is obtained. The beam patterns corresponding to different weight vectors are not related, and the peak-to-average power ratio in the angular dimension is below a preset threshold; The transmitted signals of the two branches on each antenna are superimposed and sent. 2. The method according to claim 1, wherein said selecting different weight vectors for different branches comprises: For each branch, select the phase φ(t), and obtain the weight vector w(t) from the base weight vector w through the following formula: w(t)＝diag[1 e ^jφ(t) e ^j2φ(t) … e ^j(M-1)φ(t) ]w Among them, t is the branch number, M represents the number of transmitting antennas, and diag[.] represents a diagonal matrix composed of elements in brackets; the peak-to-average power ratio of the beam pattern corresponding to the basic weight vector w in the angular dimension is lower than preset threshold. 3. The method according to claim 2, characterized in that the modulus of each component of the basic weight vector is equal. 4. The method according to claim 1, characterized in that, after superimposing the transmitted signals of the two branches on each antenna, further comprising: The continuous common channel symbols are framed, each frame includes two time-frequency blocks, and two encoded output symbols of the Alamouti code in the time-frequency dimension are transmitted respectively. 5. The method according to claim 4, wherein beamforming is performed by using the same set of weight vectors for each frame, and the same set includes two different weight vectors. 6. The method according to claim 4, wherein the phase of the next frame is obtained from the phase of the current frame and the inter-frame incremental phase value, and the next frame is adjacent to the current frame in time-frequency. 7. A signal transmitting device in a multi-antenna system, comprising: An encoding module, configured to perform Alamouti encoding on each group of common channel symbols to form two branches; The weight vector acquisition module is used to select different weight vectors for different branches, wherein the beam patterns corresponding to different weight vectors are irrelevant, and the peak-to-average power ratio in the angle dimension is lower than a preset threshold; The beamforming module is used to perform beamforming on different branches according to the selected weight vector, so as to obtain the transmission signal of each branch on each antenna; The sending module is used to superimpose and send the two transmitted signals branched on each antenna. 8. The device according to claim 7, characterized in that, the weight vector acquisition module is used to select the phase φ (t) for each branch, and obtain the weight vector by the following formula by the base weight vector w: w(t)＝diag[1 e ^jφ(t) e ^j2φ(t) … e ^j(M-1)φ(t) ]w Among them, t is the branch number, M represents the number of transmitting antennas, diag[.] represents a diagonal matrix composed of elements in brackets, and the peak-to-average power ratio of the beam pattern corresponding to the basic weight vector w in the angular dimension is lower than preset threshold. 9. The device according to claim 8, characterized in that the modulus of each component of the basic weight vector is equal.

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